[unreadable] [unreadable] The Prospective Investigation of Pulmonary Embolism Diagnosis in (PIOPED ffl) is a multicenter prospective investigation designed to give a quantitative assessment of the sensitivity and specificity of gadolinium enhanced magnetic resonance angiography (MRA) for the diagnosis of acute pulmonary embolism (PE). The study design is a prospective study of consecutive patients incorporating standardized inclusion/exclusion criteria, complete ascertainment of patient characteristics and outcomes, uniform diagnostic criteria, and unbiased central reading of imaging studies. Over a period of two years, 1256 patients with suspected acute PE will be recruited at 7 clinical centers. All patients will undergo clinically indicated tests to diagnose or exclude PE. This includes a validated clinical assessment, D-dimer by rapid enzyme-linked immunosorbent assay (ELIS A), compression ultrasound of the lower extremities, ventilation/perfusion (V/Q) lung scan, contrast enhanced spiral computed tomography (CT), and ultimately may include pulmonary digital subtraction angiography (DSA). It is expected that 317 patients will have PE and they will undergo gadolinium enhanced MRA. It is expected that 939 patients will be shown to have no PE. From among this group with no PE, 317 patients will be randomized for MRA (and venous ultrasound as well). All MRA images and all images used for the diagnosis or exclusion of PE in patients who had an MRA will be sent for blinded central readings by two readers. [unreadable] [unreadable]